Second dam on the Brandywine River being removed to restore fish passage

For centuries, dams have disrupted the natural flow of the Brandywine River and created barriers in migratory routes for fish, like the American shad, preventing them from swimming upriver to complete their life cycle. 

Brandywine River Restoration Trust, a river advocacy group, is leading a multi-year effort to restore fish passage past 11 dams on the Delaware portion of the Brandywine, which runs about 20 miles through southeast Pennsylvania and western Delaware.

The group is implementing solutions, such as fish ladders, rock ramps and dam removals, on an as-needed basis.

The first dam removal happened in 2019. And last month, the second dam removal began, as crews started dismantling the DuPont Experimental Station Dam in Wilmington, Del.

“Our objective is to enable the migration of American shad and other migratory fish up the river,” said Jim Shanahan, the executive director of the Brandywine River Restoration Trust. “To do that, we may remove dams or we may create other ways for the fish to migrate.”

Read more: The beneficiaries of removing mill dams in Delaware River watershed? ‘Fish, fish, fish’

Taking down Dam Six

The DuPont Experimental Station Dam, also referred to as Dam Six, was built in 1839. It stands approximately eight feet tall, spans 15 feet across and slopes down roughly 40 feet along the riverbed. 

“It’s going to take quite a bit of time to take this out, and we need to go very carefully to ensure there’s not a large release of sediment that would go downstream and cause problems, including potentially with the city’s water supply,” Shanahan said.

Dam Six, which is made of stone, wood and concrete, is expected to be fully removed by September. 

Because Dam Six is eight feet tall, it holds back eight feet of water. When it rains, the river rises from an already elevated level. This exacerbates flooding, which has been an issue for the nearby DuPont Experimental Station for over a century, according to Shanahan. The station, a research development facility owned by DuPont, was one of the first industrial research laboratories in the United States.

DuPont Specialty Products, the manufacturing giant that makes an array of products, including novel chemicals, fibers and plastics, agreed to help pay for the removal of Dam Six to mitigate repeated flooding of the facility.

Read more: Dam removal leads to rebirth of the Paulins Kill

This funding, combined with support from federal and state agencies, local governments, and consultants, allowed Brandywine River Restoration Trust to move forward with the removal. The cost of the removal, which is close to $1 million, includes studies and engineering plans. DuPont is contributing about a third of the total cost. 

Residents in the nearby Brandywine Falls community expressed discontent with the idea of removing the dam. At a Wilmington City Council meeting on Feb. 1, 2024, removal opponents argued that Brandywine River dams hold historic significance, add to water-related recreation activities and provide scenic beauty, The News Journal reported.

As the dam is removed, Brandywine River Restoration Trust is implementing historic preservation initiatives. Archaeological monitoring during the dismantling and opportunities for public education about the dam have helped to garner public support, Shanahan said.

Read more: Man-made lakes, loved by humans, can harm the environment

Restoring life to the river

Almost immediately after the first dam was removed from the Delaware portion of the Brandywine River in 2019, American shad were spawning in the newly opened reaches, according to studies by the Delaware Sea Grant at the University of Delaware, which helps communities protect coastal resources and works toward a more sustainable future.

“When you do have a free-flowing river, the whole ecology changes, mainly because organisms can move up and down the river more freely,” Shanahan said. “The more upriver a river is free flowing, the healthier it is and the more natural it is.”

Aquatic organisms living between dams on the Brandywine lack the adequate space to complete their life cycles. American shad, for example, are unable to swim upriver to spawn because of the barriers. The absence of these migratory fish is felt by other species that they serve as food sources for. This includes eagles, ospreys and striped bass. 

When the American shad spawn upriver in the spring, thousands of juveniles swim into the Atlantic Ocean to mature. Many juveniles are preyed on by other fish, but the American shad that survive their three to six years in the ocean return to the river when they are adults to spawn. 

Around half of the adult population die when this happens, but their decaying bodies return nutrients to the river. This benefits microorganisms and plants at the bottom of the food chain.

A bigger picture

Dam removal efforts align with a nationwide trend.

Many dams were built in the 19th and 20th centuries to harness water to power industry mills, but have since become obsolete. Because of this and the harm that such structures can cause, they are being removed across the United States at record-high rates, according to American Rivers. 

In 2024, 108 dams were removed. That was tied with 108 dams in 2019 for the highest ever in one year, according to American Rivers.

While Brandywine River Restoration Trust is not specifically in the dam removal business, the group will contribute to the nationwide trend as it works toward its mission to restore habitat in the river.

“The goal here is long-term,” Shanahan said. “To enable the [American] shad to go all the way up to Pennsylvania and then farther up into Pennsylvania as they did for centuries.”